From the prior art, a method is known for creation and visualization of optically invisible marks, according to which the surface area of the protected object (in particular, jewelry in the form of a diamond), by means of a laser beam is formed an image hidden to perception by the naked eye (the protective label), the subsequent visualization of which can be carried out by the use of appropriate optical means (U.S. Pat. No. 4,467,172).
The disadvantages of the known prior art method of visualizing hidden images include its limited field of use, For example, in marking jewelry, particularly diamonds, the geometric parameters of microstructures of the protective labels, subject to visualization by optical means, are so large that they are regarded to be a defect in the product, thereby dramatically reducing its aesthetic properties and value.
There is also a way of creating and visualizing an optically invisible mark, according to which an optically invisible marking image is created on the surface of the object by modifying at least one area of the surface, followed by visualization of the marking image microstructure by etching and subsequent viewing of the image using the strong optical or electron microscope (RU, No. 2073270, C1).
The disadvantages of this known prior art method of creating and visualizing an optically invisible mark, as in the previous case, include the limited field of application because of its applicability only to the special polymer materials in the form of films, as well as the inability to visualize the latent marking images without the use of powerful microscopes.
In addition, the known method does not save the label optically invisible after the first visualization (i.e. visualization by etching).
The closest to the claimed invention is a method of creation and visualization of an optically invisible mark, according to which the surface of the object is first polished. On the polished surface, an optically invisible marking image is formed by modifying at least one area of the surface. As a result of surface modification, the surface energy of modified sites changes. Said marking image is then visualized by means of establishing a meta-stable environment in the vicinity of the aforementioned surface of the object. By means of said environment, the marking image is produced in the form of distinguished structures formed by stable phase particles of the meta-stable environment at the sites of the object surface having different surface energy. (WO 02/089041, C1, EP 1391841).
The disadvantages of the known method include a relatively low contrast of the visually perceived marking image because of the small difference in the surface energy of modified and un-modified surface areas, and hence the image quality being highly dependent on the investigated surface contamination.
Furthermore, during repeat visualization of tags, the marking image may be overlapped by the image of a structure formed by the merger of several centers of condensation and the emergence of new centers during evaporation of the condensate from the previous visualization (FIG. 1). That is, the relatively uniform layer of surface contamination micro-particles (which are always present in the real world visualization) is modified in the event of condensation of droplets on the surface and evaporation of condensate with the formation of randomly distributed micro-particle islets on the examined surface. In the subsequent visualization, these micro-particle islets may become additional functional centers of condensation, distorting the marking image.